1. Field of the Invention
One of embodiments of the present invention relates to a semiconductor element such as a transistor and/or a semiconductor device at least part of which is formed using the semiconductor element. For example, an active element including an oxide semiconductor is described as the semiconductor element, and a display device including the active element is described.
2. Description of the Related Art
Although transistors including amorphous silicon have been used for conventional display devices typified by liquid crystal televisions, an oxide semiconductor has attracted attention as a material which replaces a silicon semiconductor in order to form transistors. For example, an active matrix display device is disclosed, in which an amorphous oxide containing In, Ga, and Zn is used for an active layer of a transistor and the electron carrier concentration of the amorphous oxide is less than 1018/cm3 (see Patent Document 1).
However, some problems of a transistor including an oxide semiconductor have been pointed out. One of the problems is the stability of the characteristics, and it is pointed out that the electric characteristics of the transistor are changed by irradiation with visible light and ultraviolet light.